Honeycomb structures have been used in, for example, an exhaust gas purifier of a heat engine (e.g. an internal combustion engine) or a burner (e.g. a boiler), or in a reformer of a liquid fuel or a gaseous fuel. It is known that honeycomb structures are also used to capture and remove a particulate substance present in a particle-containing fluid, for example, an exhaust gas emitted from a diesel engine.
In the honeycomb structure used for such a purpose, the sharp temperature change of exhaust gas and the local heating tend to make non-uniform the temperature distribution inside the honeycomb structure, which has caused problems such as crack generation in honeycomb structure and the like.. When the honeycomb structure is used particularly as a filter for capturing a particulate substance in an exhaust gas emitted from a diesel engine, it is necessary to burn the fine carbon particles deposited on the filter to remove the particles and regenerate the filter and, in that case, high temperatures are inevitably generated locally in the filter; as a result, a big thermal stress and cracks have tended to generate.
Honeycomb structures have become larger depending upon the application purpose. Hence, it is known to produce a larger honeycomb structure by bonding a plurality of honeycomb segments 1, as shown in FIG. 12. In this case as well, it is necessary to reduce the thermal stress generated.
As a means for reducing the thermal stress, there is disclosed in, for example, U.S. Pat. No. 4,335,783, a process for producing a honeycomb structure, which comprises bonding a large number of honeycomb parts using a discontinuous adhesive.
Also in JP-B-61-51240 is proposed a heat shock-resistant rotary regenerating heat exchanging method which comprises forming, by extrusion, matrix segments of honeycomb structure made of a ceramic material, firing them, making smooth, by processing, the outer peripheral portions of the fired segments, coating the to-be-bonded areas of the resulting segments with a ceramic adhesive having, when fired, substantially the same mineral composition as the matrix segments and showing a difference in thermal expansion coefficient, of 0.1% or less at 800° C., and firing the coated segments.
Also in a SAE article 860008 of 1986 is disclosed a ceramic honeycomb structure obtained by bonding cordierite honeycomb segments with a cordierite cement.
Further in JP-A-8-28246 is disclosed a ceramic honeycomb structure obtained by bonding honeycomb ceramic members with an elastic sealant made of at least a three-dimensionally intertwined inorganic fiber, an inorganic binder, an organic binder and inorganic particles.
The aim of the present invention is to provide a honeycomb structure which hardly generates cracks caused by the thermal stress appearing therein during the use and which is superior in durability.